In agriculture it is a well known practice to bale crop material using balers that create round or cylindrical bales. It is also a common practice to store such bales outdoors where they are exposed to the elements of rain and snow. Nearly all, round bales stored outside without some form of protection from rain and/or snow will experience mold growth in the outer rind of the bale. The depth to which the mold appears is dependent on many factors but the one critical factor is the depth to which water penetrates the baled crop.
The potential benefits of applying mold inhibiting preservatives to hay either during a baling process or to the finished bale are well known and include (a) permitting the hay to be baled and stored at higher moisture contents without spoilage, thus reducing field losses and making the hay making operation less dependent on favorable weather conditions; (b) improved palatability and digestibility; and (c) higher nutrient content. The relative importance of these benefits varies with the crop being treated and the preservative used.
Accordingly, preparations of buffered propionic acid or anhydrous ammonia are sometimes applied to the hay at the time of baling to prevent bacterial and mold growth. Typically, these preparations are applied to the entire bale as it is being formed or injected into the bale after formation. The problem with using such preservatives is that they can be corrosive, difficult to apply, and evaporate with time with the result that their effectiveness is diminished.
Recently new preservatives have been developed that are less volatile and more stabile than propionic acid or anhydrous ammonia. The problem is that these new proprietary preservatives can be costly to apply to the entire bale. Because of this, there is a desire to apply the preservative only to the outer rind of the bale to a predetermined depth, so as to assure that the outer rind of the bale is adequately treated while still conserving costly preservative preparations.